Preparation of metallic particles for electrokinetic or electrostatic deposition

Abstract

Metallic particles for electrokinetic or electrostatic deposition, and a method for making such particles, comprising metallic particle bodies, an organic acid film on the particle bodies, and a charge director adhered to the organic acid film.

1. A method for preparing metallic particles for electrokinetic or electrostatic deposition comprising the steps of:
 contacting the metallic particles with a fully concentrated organic acid to form an organic acid surface film on the particles wherein the organic acid is selected from the group consisting of acetic acid, dicholoroacetic acid, trichloroacetic acid, propionic acid, maleic acid, glutaric acid, and methacryclic acid; and wherein the particles are solder metal particles; and 
 contacting the metallic particles with a charge director medium which adheres to the organic acid surface film to impart an electrical charge to the particles; 
 wherein the contacting the metallic particles with the fully concentrated organic acid comprises contacting the metallic particles with the fully concentrated organic acid in a ratio of weight of organic acid to weight of metallic particles in a range between about 0.2:1 to about 2:1. 
 
     
     
       2. The method of  claim 1  wherein the particles are selected from the group consisting of Sn particles and Sn alloy particles. 
     
     
       3. The method of  claim 1  wherein the particles are selected from the group consisting of Sn particles, Sn/Pb particles, Sn/Ag/Cu particles, Sn/Ag particles, Sn/Cu particles, Sn/Ag/Bi particles, Sn/Bi particles, and Sn/Pb/Bi particles. 
     
     
       4. The method of  claim 1  further comprising the steps of decanting excess organic acid and washing the particles after the contacting the metallic particles with the organic acid and before the contacting the particles with the charge director medium. 
     
     
       5. The method of  claim 4  wherein washing the particles comprises washing the particles with isopropyl alcohol at least twice and washing the particles in an isoparaffin solution at least twice. 
     
     
       6. The method of  claim 1  wherein the charge director medium is a solution comprising a charge director selected from the group consisting of barium petronate, calcium petronate, copper napthenate, and aluminum stearate. 
     
     
       7. The method of  claim 1  wherein the metallic particles have a particle size between about 0.5 micron and about 50 microns. 
     
     
       8. The method of  claim 1  wherein the metallic particles have a particle size between about 1 micron and about 100 microns. 
     
     
       9. The method of  claim 1  wherein the metallic particles have a particle size between about 50 microns and about 500 microns. 
     
     
       10. The method of  claim 1  wherein the metallic particles have a particle size between 100 microns and 1 mm. 
     
     
       11. A method for preparing metallic particles for electrokinetic or electrostatic deposition comprising the steps of:
 contacting the metallic particles with a fully concentrated organic acid to form an organic acid surface film on the particles wherein the organic acid is selected from the group consisting of acetic acid, dicholoroacetic acid, trichloroacetic acid, propionic acid, maleic acid, glutaric acid, and methacryclic acid; and wherein the particles are selected from the group consisting of Sn particles, Sn/Pb particles, Sn/Ag/Cu particles, Sn/Ag particles, Sn/Cu particles, Sn/Ag/Bi particles, Sn/Bi particles, and Sn/Pb/Bi particles; and 
 contacting the metallic particles with a charge director medium which adheres to the organic acid surface film to impart an electrical charge to the particles; 
 wherein the contacting the metallic particles with the fully concentrated organic acid comprises contacting the metallic particles with the fully concentrated organic acid in a ratio of weight of organic acid to weight of metallic particles in a range between about 0.2:1 to about 2:1. 
 
     
     
       12. The method of  claim 11  wherein the charge director medium is a solution comprising a charged director selected from the group consisting of barium petronate, calcium petronate, copper napthenate, and aluminum stearate. 
     
     
       13. The method of  claim 11  further comprising the steps of decanting excess organic acid and washing the particles after the contacting the metallic particles with the organic acid and before the contacting the particles with the charge director medium. 
     
     
       14. The method of  claim 13  wherein washing the particles comprises washing the particles with isopropyl alcohol at least twice and washing the particles in an isoparaffin solution at least twice. 
     
     
       15. The method of  claim 11  wherein the metallic particles have a particle size between about 0.5 micron and about 50 microns. 
     
     
       16. The method of  claim 11  wherein the metallic particles have a particle size between about 1 micron and about 100 microns. 
     
     
       17. The method of  claim 11  wherein the metallic particles have a particle size between about 50 microns and about 500 microns. 
     
     
       18. The method of  claim 11  wherein the metallic particles have a particle size between 100 microns and 1 mm.